<!DOCTYPE html>
<html>
<head>
<style type="text/css">
#a {
 height: 20px;
 background-color: red;
 margin-bottom: 20px;
}
#b {
 height: 20px;
 background-color: blue;
 margin-top: 10px;
 margin-bottom: 10px;
 position: relative;
 top: 40px;
}
#c {
 height: 20px;
 background-color: green;
 margin-top: 20px;
 position: relative;
 top: -40px;
}
</style>
</head>
<body>
<div id="a"></div>
<div id="b"></div>
<div id="c"></div>
</body>
</html>
